The indicated power of an internal combustion engine at a given speed is proportional to the mass flow rate of air. Thus, inducting the maximum air mass at wide-open throttle or full load and retaining that mass in the cylinders will provide the greatest volumetric efficiency. Supercharging the engine is one way to increase the air flow and hence power density. This can be done by turbocharging, which requires external apparatus, or by resonant tuning the induction system over a wide engine speed range and/or using inertial or ram tuning at the higher engine speeds.
The resonant effect occurs as a result of the pressure waves set up by each cylinder reflected from the inlet valve back towards the intake which can be controlled to reinforce the process, and, therefore, become tuned over a wide engine speed range, which will increase the inducted air mass.
The use of resonant tuning and the inertial effect to supercharge an engine is known in general. Wide-open throttle output of an engine with a fixed geometry intake system is characterized by one or more local maxima in torque due to tuning of the induction system in a very narrow speed range. Various variable intake geometry schemes have been suggested as a means to produce a broader torque curve with improved performance over the entire speed range. These devices use adjustable components to change the primary runner geometry to affect the natural frequency of the induction system and thereby provide tuning over a broader engine speed range.
The invention utilizes both resonant and inertial tuning to maximize the mass input of air into the engine cylinders. It is known in the prior art to utilize resonant tuning to supercharge an engine by changing the effective length of the intake runner that provides the mass flow of air to the cylinders. The inertial effect at higher engine speeds is also known. However, the prior art does not provide a construction that utilizes both resonant and inertial tuning in the manner to be described in combination to maximize the mass intake of air to provide the most efficient supercharging.